1. Field of the Invention
This invention deals with improvements in CACing, a method of increasing productivity of mushroom beds by shortening the time required to produce a new crop of mushrooms.
2. Review of Related Art
Mushroom production proceeds via a sequence of steps. First, the nutritive medium (compost) is inoculated with mushroom mycelia by distributing particulate material colonized with mushroom mycelia (spawn) through it, and then the compost is colonized by the mycelium. Mushroom spawn is generally made from sterilized grain that is inoculated with pure cultures of the desired mushroom strain. Next, the colonized compost is covered by a layer of nutrient poor material (easing). The mycelium proceeds to colonize this layer, and once the easing layer is colonized, the mycelium in this nutrient poor environment produces fruiting bodies. These fruiting bodies are harvested and sold as commercial mushrooms.
The time-consuming stages of mushroom production are the periods when the farmer is waiting for the mycelia to colonize a new material. One way that has been used to accelerate the process is to mix precolonized material, such as colonized compost, into the casing layer on top of the compost in the bed, after the compost layer is colonized with mushroom mycelia. Overall production time is reduced, because growth of the mycelia into the casing starts at many points throughout the casing layer rather than just at the interface with the colonized compost. By including a small amount of colonized material in the nutrient-poor casing layer, the casing layer is colonized more quickly and the farmer can produce a crop in a shorter time, thereby increasing his capacity without capital investment. This procedure is referred to as "CACing" (Compost At Casing).
Although the CACing procedure accelerates production to increase capacity for a fixed volume of mushroom bed, the colonized compost that is added to the casing layer as inoculum must come from somewhere. If it comes from the farmer's own beds, then he loses capacity equal to the amount of bed volume used to provide the casing inoculum. Another problem with using locally developed inoculum is controlling quality. If the compost is weakly colonized, then the CACing procedure will not increase the rate of colonization enough to compensate for the loss of bed capacity. Even worse, because this supplemental inoculum is not sterilized, it has the potential for spreading infection by contaminating organisms throughout the mushroom house thereby reducing the productive capacity of the house.
Some farmers have attempted to solve these problems by inoculating the casing layer with the same spawn that is used to inoculate the compost layer. Spawn for inoculating the compost layer is produced by mixing mushroom mycelia with sterile grains and incubating to allow colonization of the grain. The grain spawn has a consistent level of live mycelial content, but it has relatively high nutrient content (contributed by the grain). In order to be effective, the inoculum must be supplied at relatively high levels and the resultant nutrient level in the casing layer inhibits formation of mushroom primordia (fruiting bodies). It also increases the potential for growth of contaminating organisms by providing them with nutrients that are normally absent from the casing layer.
Spawn makers have tried to produce a "casing spawn" which contains low levels of nutrients and has been sterilized to eliminate pathogens and pests, but the products currently available are not effective. Stoller, U.S. Pat. No. 3,828,470, teaches spawn in which the cereal substrate has been diluted with an inorganic material containing calcium carbonate or an organic flocculating agent. Romaine, et al., U.S. Pat. No. 4,803,800, teaches production of casing spawn by encapsulation of the nutrients in a hydrogel polymer.